Transducers can be classified based on various criteria given below-
1. Based on the quantity to be measured
- Pressure transducers (e.g. a diaphragm)
- Temperature transducers(e.g. a thermocouple)
- Displacement transducers (e.g. LVDT)
- Flow transducers
2. Based on the principle of operation
- Photovoltaic ( e.g. a solar cell )
- Mutual Induction
3. Based on Whether an External Power Source is required or not
Transducers that do not require any power source for their working are active transducers. They work on the principle of energy conversion. They produce an electrical signal proportional to the input. A common example is a thermocouple.
This type of transducer requires an external power source to operate. With the small change in capacitance, resistance or any other electrical parameters, passive transducers create the output signal.Then it is converted into the equivalent voltage or current signal. A photocell is an example of a passive transducer.